An engine, particularly a 4-cycle engine, is equipped with an intake valve and an outlet valve for the purposes of taking air into a combustion chamber and discharging exhaust therefrom. As for systems of these valves, there are a side valve system, an overhead valve system, etc. Some of the valve gears for actuating these valves, for example, those for actuating valves of an overhead valve system, include a seesaw type rocker arm or a swing type rocker arm.
A seesaw type rocker arm is oscillatably supported at an intermediate portion thereof by a rocker shaft. The seesaw type rocker arm is slide contacted at one end thereof with a cam of a cam shaft and abutted at the other end against a valve stem. On the other hand, a swing type rocker arm is supported at one end thereof by a pivot portion. The swing type rocker arm is slide contacted at an intermediate portion thereof with a cam of a cam shaft and abutted at the other end against a valve stem. Some of the valve gears for actuating an overhead type valve are of direct drive type, in which a valve stem is directly driven by a cam of a cam shaft.
One example of the valve gears mentioned above are shown in FIGS. 4 through 6. In FIG. 4, the numeral 202 denotes an engine, and 204, a cylinder head. The cylinder head 204 of the engine 202 has a combustion chamber 206 defined by a cylinder block and a piston (not shown), and an intake port 208 and an outlet port 210 communicating with this combustion chamber 206. An intake valve stem 216 and an outlet valve stem 218 of an intake valve 212 and an outlet valve 214 for opening and closing the intake port 208 and the outlet port 210 are provided with an intake valve spring 220 and an outlet valve spring 222, and also with an intake valve stem abutment portion 224 and an outlet valve stem abutment portion 226, respectively.
In a valve gear 230 disposed in a valve gear chamber 228 of the cylinder head 204, a cam shaft 232 to be rotated by the engine 202 is supported on the cylinder head 204 through a cam cap 234, and a swing type intake rocker arm 240 and a seesaw type outlet rocker arm 242 are actuated by an intake cam 236 and an outlet cam 238 mounted on this cam shaft 232. The swing type intake rocker arm 240 is provided at one end thereof with a portion 246 swingably supported by a hydraulic valve adjuster 244 for adjusting a valve clearance. The arm 240 is provided at an intermediate portion thereof with a slide contact portion 248 to be slide contacted with the intake cam 236, and at the other end thereof with an abutment portion 250 to be abutted against the intake valve stem abutment portion 224. The seesaw type outlet rocker arm 242 is provided at an intermediate portion thereof with a portion 254 oscillatably supported by a rocker shaft 252. The arm 242 is provided at one end thereof with a slide contact portion 256 to be slide contacted with the outlet cam 238, and at the other end thereof with a hydraulic valve adjuster 258 for adjusting a valve clearance.
In FIG. 4, the numeral 260 denotes a head cover. The head cover 260 is provided with a breather chamber 262 defined therein in such a manner as to be opposite the valve gear chamber 228 and also with a breather pipe 264 through which this breather chamber 262 is communicated with an intake system.
In the valve gear 230 of the engine 202, the intake rocker arm 240 and the outlet rocker arm 242 are actuated for oscillation by the intake cam 236 and the outlet cam 238 of the cam shaft 232 rotated by the engine 202. The intake rocker arm 240 is oscillated by the intake cam 236 of the cam shaft 232 about the hydraulic valve adjuster 244 disposed at one end thereof and moves the intake valve stem 216 in the axial direction with the abutment portion 250 disposed on the other end thereof, to thereby open and close the intake valve 212. On the other hand, the outlet rocker arm 242 of the valve gear 230 is oscillated by the outlet cam 238 of the cam shaft 232 about the rocker shaft 252 disposed at an intermediate portion thereof and moves the outlet valve stem 218 in the axial direction with the hydraulic valve adjuster 258 disposed on the other end thereof, to thereby open and close the outlet valve 214 disposed at the outlet port 210.
One example of the valve gear mentioned above is disclosed in Japanese Utility Model Early Laid-open Publication No. Hei 1-136611. The one disclosed in this publication is constituted such that a swing type rocker arm is swingably supported at one end thereof by a hydraulic valve adjuster, the arm being slide contacted at a roller on an intermediate portion thereof with a cam of a cam shaft and abutted at the other end thereof against a valve stem abutment portion, wherein a hole for discharging a mixture of air and lubricating oil formed in a plunger of the hydraulic valve adjuster is formed in such a manner as to be directed in a direction of the abutting surfaces between the cam of the cam shaft and the roller.
In FIG. 4, the hydraulic valve adjuster 244 pivotally supporting the one end of the intake rocker arm 240 and the hydraulic valve adjuster 258 abutted at the other end of the outlet rocker arm 242 against the outlet valve stem 218 are operated by being supplied with lubricating oil through lubricating oil paths 266 and 268, respectively, and they, in turn, discharge a mixture of air and lubricating oil into the valve gear chamber 228 through discharging holes 270 and 272, respectively.
However, in the conventional arrangement, when a mixture of air and lubricating oil is discharged into the valve gear chamber 228, the mixture reaches so far as the breather chamber 262 of the head cover 260 with the result that the air and lubricating oil are discharged through the breather pipe 264 without being separated into air and liquid. Furthermore, when the mixture is discharged without being separated into air and liquid, lubricating performance is lowered owing to the resultant decrease in lubricating oil in chamber 228.
Therefore, the system in the above-mentioned publication attempts to improve the lubricating performance by forming the hole for discharging the mixture in the plunger of the hydraulic valve adjuster in such a manner as to be directed in the direction of the abutting surfaces between the cam of the cam shaft and the roller of the swing type rocker arm and discharging the mixture toward the abutting surfaces. However, this particular arrangement has problems in that the distance from the discharging hole to the abutting surfaces between the cam and the roller is long because the hole for discharging the mixture is formed in the plunger of the hydraulic valve adjuster. Therefore, the mixture is uselessly dispersed before it reaches the abutting surfaces and cannot be effectively brought into contact with the abutting surfaces. As a result, favorable lubrication is unobtainable. In addition, the mixture is not adequately separated into air and liquid.
As shown in FIGS. 5 and 6, in case the hydraulic valve adjuster 258 for adjusting valve clearance is disposed at the other end of the seesaw type outlet rocker arm 242, heretofore, the terminal end of the hole 272 for discharging the mixture is formed in such a manner as to be directed upwardly within the valve gear chamber 228. Accordingly, this also had inconveniences, as in the system of the above publication. For example, since the distances from the discharging hole 272 to the outlet cam 238 and to the slide contact portion 256 to be slide contacted with the outlet cam 238 are long, the mixture is uselessly dispersed before it reaches the outlet cam 238 and the slide contact portion 256, and the mixture cannot be brought into contact with the outlet cam 238 and the slide contact portion 256 sufficiently. As a result, favorable lubrication is unobtainable. In addition, the mixture is not adequately separated into air and liquid.
One object of the present invention is to realize a valve gear lubricating device of an engine which is capable of bringing a mixture of air and lubricating oil discharged from a hydraulic valve adjuster into colliding contact with a moving part of a valve gear without uselessly dispersing the mixture, thereby separating the mixture into air and lubricating oil by means of this colliding contact with the moving part, favorably lubricating the moving part of the valve gear by such separated lubricating oil, preventing the lubricating oil from being discharged, and avoiding deterioration of lubricating performance.
According to the present invention, there is provided, in an attempt to obviate the above inconveniences and achieve the above object, a valve gear lubricating device for lubricating a valve gear of an engine, including a cam shaft being rotated by said engine, a rocker arm oscillated by a cam of said cam shaft, a slide contact portion formed on one end of said rocker arm and being slide contacted with said cam, and a hydraulic valve adjuster mounted on the other end of the rocker arm and adapted to adjust a valve clearance of said engine, wherein said valve gear lubricating device is characterized in that said rocker arm is provided with a mixture passage through which a mixture of air and lubricating oil discharged from said hydraulic valve adjuster flows, said mixture passage being opened up at a terminal end thereof proximate to a moving portion of said valve gear.
According to the constitution of the present invention, by virtue of such arrangement wherein the mixture passage for carrying therethrough the mixture of air and lubricating oil discharged from the hydraulic valve adjuster is mounted on the rocker arm and opens at a terminal end thereof proximate to the moving part of the valve gear, the mixture can be brought into colliding contact with the moving part of the valve gear without useless dispersing thereof.